17-year cicadas emerging in Naperville this spring

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This spring, the Naperville area will experience an insect influx that only comes around once every 17 years.

“It’s an exciting year for cicadas up here in Chicagoland and at the Arboretum,” said Stephanie Adams, The Morton Arboretum’s plant health care leader. “We’re going to be experiencing a 17-year cicada, while further south in Illinois, we’re also going to have a 13-year cicada.”

The 13-year cicada is referred to as Brood XIX, and the 17-year cicada is called Brood XIII. For the first time since 1803, both broods will emerge at the same time in pockets around the country, which experts are calling “cicada-geddon.”

“There’s going to be space right around Springfield that they’re going to be overlapping,” said Adams. 

Cicadas to emerge from underground in droves

Scientists estimate there can be 1.5 million cicadas per acre in forestry areas.

“Cicadas will start emerging; they’ll be crawling up and burrowing through the soil,” said Adams. “That usually begins when the soil temperature and their bodies are at least 68 (degrees Fahrenheit), and that is measured eight inches below the soil line.”

According to the Arboretum, cicadas live approximately 99 percent of their lives underground in nymph form and only live two to four weeks above ground.

“Once the cicadas start emerging from the soil, they will usually crawl up a vertical surface and shed their exoskeleton, which allows them to grow into their adult form,” said Adams. “These exoskeletons are really great sources of nutrients and minerals that through their decomposition, actually helps build the soil.”

Protecting your plants from cicadas

Adams said female periodical cicadas target small trees and bushes to reproduce, which can negatively impact local vegetation.

“When the females do lay their eggs, they cause some damage on the underside of the branches,” said Adams. “What happens is the female will take her ovipositor and basically cuts slits into the stems to lay the eggs.”

In preparation for the cicadas, the Arboretum will cover 500 of its trees with tulle, or polyester nylon fabric. Adams recommends locals protect their plants in the same fashion.

“The trees that you want to protect are either small, newly planted, or maybe struggling in some way just so they don’t get additional stress,” said Adams. “It’s basically a barrier method of the cicadas being able to get access to the plant. Just wrap the tree so there (are) no holes larger than a half-inch. We are recommending to put the tulle over trees starting in early May and keeping it on for six to eight weeks to protect the trees.”

Adams warns putting tulle on too early can make for an unsightly tree throughout the summer months.

“You want to be careful that the leaves that are just emerging and some of the flower buds, you want to minimize damage to them,” said Adams. “Hopefully by early May, most trees that are going to be covered will already have their leaves emerged and hardened off, which means they’re fully expanded.”

Despite cicadas’ danger to trees, Adams says not to worry if your pet eats one of the bugs or its exoskeletons.

“It will not harm your pets,” said Adams. “They may get an upset stomach like they would over-eating anything.”

No pesticides on cicadas

The Morton Arboretum advises homeowners not to use any pesticides on plants.

“The (cicada) emergence is going to be very high, and it’s going to be so staggered over time,” said Adams. “Any pesticides will also affect the beneficial insects and other, non-harmful insects in our ecosystem, which will actually cause a bigger problem.”

The annual, or dog-day cicadas will still make their rounds in late July and August. But Napervillians will get to experience the loud songs and unique phenomena of the 17-year variant soon.

“They’re part of our natural ecosystem,” said Adams. “They don’t harm people. They don’t have stingers, they don’t bite. It’s a neat opportunity to just walk up, grab one, and really take a look at it and appreciate it.”

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